Air duct assembly



Sept. 28, 1943. F. J. TOWNSEND AIR DUCT ASSEMBLY Filed Dec. 8 1942' 2 Sheets-Sheet 1 FRANK J. TOWNSEND y 7121s a/ZZ'ar-neys' P 28,.1943- F. J. TOWNSEND 2,330,763

AIR DUCT AS SEMBLY Filed Dec. 8, 1942 2 Sheets-Sheet 2 JFzverziar FRANK J. TOWNSEND transverse or corner joint, and the Patented Sept. 28, 1943 UNITED STATES PATENT? OFFICE 2,330,763 AIR DUCT ASSEMBLY 7 Frank J. Townsend,Pelham Manor, Y. Application December 8, 1942, Serial No. 463,282

11 Claims. (Cl. 138-78)" This invention relates to heating, ventilating and air-conditioning ducts, and more particularly to assemblies for such ducts where the ducts are made of composition board. One object of the invention is toproduce an assembly for ducts made of composition board I which requires only the minimum amount of metal and which is simple and quick toassemble on the job. It is characteristic of the invention that the assembly contains metal stripsprojecting outwardly fro-mthe edges of the boards and bent t interlock the boards. i

In the drawings: I Figure 1 is a sectional view in perspective of an edge ofa top board of a duct with one member of my novel corner assembl attached thereto;

Figure 2 is a similar view of the edge of a side board with the other member of my novel corner assembly attached thereto; 7

Figure 3 is a sectional view in perspective of the novel corner of Figures 1 and 2 assembled;

Figure; is a sectional View in perspective of my novel transverse joint assembly, the dotted lines showing the position of the; return bend beforeit is folded down; 1 I

Figure 5 is a sectional view taken on the line 55 of Figure 4, showing the button punch after the parts are assembled; I

Figure 6 is a view in perspective of one end of a female joint and its relation to a corner; while Figure 7 is a view of an assembled duct made in accordance with my invention.

In air ducts for heating, ventilating or airconditioning, it has been customary for many years to make the ducts of sheet metal. Now-adays, however, it is frequently desirable to use non-metallic sheet material such as asbestos or other molded or composition boards, and to keep the metal in the finished duct to a minimum. Heretofore, such composition board ducts have had to be made to "order and fitted on the job, with consequent expense and delay. Furthermore such prior constructions were not convenient for manipulation on the job, requiring cutting to size, punching of metal, the use of nails, etc. The new assembly which I have devised is a great improvement inthat it eliminates all punching of holes in metal on the job and the use of Wood and nails. Its assembly is very rapid, being done merely by sliding the parts together.

Referring to the drawings, it will be seen that air ducts of the type referred to are customarily square or oblong in cross-section, each board.

being the full width of the top or bottom or the full height of a side. The joints betweenthe ends of the boards in the top and bottom are offset or broken with relation to the joints in the sides. Each joint is made by metal strips projecting from each board edge, whether it be a interlocking is by bends in the strips. l

It is characteristic of thepresent invention that each corner edge is so constructed in the shop that on'the job it is necessary merely to slide the two parts lengthwise of the joint until they are opposite each other, in order to complete the assembly. As soon as the parts are thus slid together the corner or right-angle joint is locked and is readyto resist any stress except one tending to slide the joint apart in the direction in which it was-assembled. The duct is thus built rapidly and Without any operations such as boring holes through metal, screwing screws or driving nails.

In the case of butt or straight-line joints, since all the sliding operations in assembling are longitudinal of the duct and these butt joints lie transversely to the length of the duct, it follows that the sliding of a board into juxtaposition with the previous board in that face of the duct does not leave the two anchored together as in the case of the right-angle or corner joint. To give added strength and rigidity by anchoring these two butt ends together, it is merely necessary with the novel straight-line joint that I have devised, to make a simple bending operation on the job," and button-punch the seam-thus assembled.

Turning now to the detailed construction, I shall first explain the novel right-angle or corner lock joint which I have devised, Where rigidity is obtained merely by sliding the new board in position by movement longitudinally of the seam. This joint of course is the one which forms a corner of the finished duct, and one is provided at each of the four corners. The strips on the boards constituting the vertical sides of the ducts are preferably female members, and the strips on the top and bottom are preferably the male members, in my novel structure. The female member consists of two parts-an outside slide corner I!) and an inner back-up strip l2, one on the outside of the asbestos side board l3 and oneon the inside, the two being held in position by screws I3. These two members of the corner joint are assembledwith the asbestos side board l3 in the shop and are uniform for the longitudinal edges provide interlocking with the male member on the top board 14, this return bend extending back almost to the outer or upwardly extending leg l9. This return bend lies between the inward bend Hand the board. It is spaced from the inward bend a distance sufilcient to permit passagebetween the two bends of one thickness of the material of which the male part of the corner is composed. The back-up strip l2 consists of a right-anglepiece of material with one leg 20 held against the inner face of the asbestos board l3 and the other leg 2| flush with and constituting an inward extension of the edge of the board. As can be seen from Fig. 3 of the drawings, the board l4 constituting the top of the duct wall, when the parts are slid together, lies on top of the edge of the side board I3, and .on the upper or horizontal arm 2| of this supporting strip 12.

Turning now to the cooperating male strip on the board which is to be the top of the duct, it will beseen that it is a slide H made out of a single piece of material fastened on the upper face of the top boardl lp This consists of a strip extending along the edge of the board, projecting a very small fraction of an inch beyond the edge of the board, and then havinga return bend 22 tiontc the side edge of the board and cleat that they prevent outward movement of the top board or inward movement of the upperedge of the side board: In the form shown in the drawings this distance is just greater than the total distance from theoutside of the side board to the inner z;-

end of the horizontal supporting leg 2! of the back-up strip on the side board. These screws 15; are longer than the thickness of the board and project through it for a distance of say The corner or right-angle joint can be ase seinbled by sliding the second board into position no matter which boardis in position first, partly becausewith the exception of the beginning of the duct, the joints are broken or offsetto insure that the board first slid into position will be held in proper position by the duct, so that it need not be; held in by hand. As canbe seen-from the assembled view of Fig. 3, when the return bend 22 of the top slide H slides in between the return bend it and the inward bend H of the outside strip, the top board will come to rest on the edge 'of the side-board and the back-up strip. The

key to the structural strength of this right-angled or'edge joint is primarily the relation of the over-length screws l5 to the back-up strip 52. -It will be observed that these screws are practically touchingor, if desired, can actually be made to touch-the edge of the back-up strip.

This serves to prevent'collapse of the corner. The" screws transmit such stress or dislocation directly to the side board 13 without any adverseleverage, i. e., in direct line. The side board of course cannot pull'outwardly from the top of the duct because of the interlocking return bonds of the male and female members, and the fact that the male strip lies under the inward bend of the female strip provides-a direct-line locking of the top board against movement upwardly away from the side board. Of course the topboard cannot collapse downwardly because it -is resting on the edge of the side board and the horizontal leg of the. support portion. The screws prevent the top-board from moving outwardly with relation to the side board, or the side 'bard inwardly with relation to the top board.

clarity.

It will thus be seen that the joint is adapted to resist stress in.either direction in direct line, so that full strength is obtained in spite of the utter simplicity of assembly of the corner.

. Similarly the straight-line or butt joints, which are found transversely across each face of the duct at the end of each board, are structurally strong joints with strips adapted to form bends which enable simple and rapid assembly on the job. Basically this joint comprises a strip on the edge of each board to be joined, the strip projecting upwardly from its board on the side which isto be outside the duct. The strip of one board is lower than the other and constitutes the male member. The female or higher stripon the edge of the other board is adapted to be folded over the male member in'a return bend 24 and buttonpunched at 25, if desired, so that the punching extends into the reverse bend, the male member and the main portion of the female member (see Figsj l and 5). I prefer to make these strips in the strong and rigid but simple manner which I shall now set forth.

The female member consists of two strips of sheet material, such for example as sheet metal. One strip 26 is attached on one face of the board, and the other strip 2! ends on the other face. The two legs on the faces of the board may be held in place by screws 28 (put in at the shop), each holding both legs. The two thicknesses are bent at right angles to the fastened legs, the bends being opposite the end cf the board, one thickness 2c of course extending across the end of the board. If desired, the two thicknesses of metal may be spot-welded together at 3! where they overlap. Preferably the leg 2'! coming from the inside of the board terminates at the height of the male member (to be described), and it is the member 26 on the outside of the board which performs the return bend.

The male member 39 can be similarly constructed or made out of one pieceof metal folded double, as shown. When the two butts are brought into juxtaposition, the female member will extend far enough above the male member to permit its being bentdown over the male member sufficiently to form the thicknesses of metal being button-punched together.

Thenovelty of this straight-line joint, aside from its part in the broad return bend principle, lies in the doubled construction embracing the edge of the board and held with screws through both layers; the shaping of the female member so that-it can be folded over the male member and button-punched to it; and the spot-welding of the twolayers of metal on the female member to give it strength.

As can be seen in Fig. .6, the ends of the strips at the transverse joints are notched. Specifically the endof each leg coming from the inner face interfittings .enablethe boards to rest on each other throughout their length. Fig. '7 shows the general relation of the boards. and seams, the view size of the metal parts being enlarged for The simple, strong. and practical construction .above described not only permits simple and rapid assembly onthe job, as above set forth, but

I also is susceptible of being prepared easily in the shop preparatory tobeing sent to the job. It will be noted that the sheet metal assembly which I' have devised for composition ductwork requires only the minimum weight of metal and makes nearly every piece of metal perform two functions, but it does not inject into the construction impossible or undesirable to use an all-metal duct, will be obvious to all.

I claim: i 1. An air duct for heating, ventilating or airconditioning systems, comprising non-metallic boards for the top, bottom and sides, in combination with one or more metal strips mounted on each edge of said boards projecting outwardly at the edges of the boards, whereby said'boards are adapted to be interlocked by bends in said projecting strips, the metal strips for the corners of the duct having reverse bends adapted to be interlocked by sliding the boards longitudinally relatively to each other, the reverse bend on one of the complemental strips overlying and being spaced from the edge of its own board to receive on it the board of the other strip.

2.An air duct for heating, ventilating or air conditioning systems, comprising non-metallic boards for the top, bottom and sides, in combina- 'tion with metal slide corners adapted to lock the longitudinal edges of the boards, said corners each comprising complemental metalstrips having return bends adapted to interlock whenythe boards are slid longitudinally with relation to each other, the strip on one of the boards being adapted to receive the other board between it and the edge of its own board.

3. An air duct for heating, ventilating or airconditioning systems, comprising non-metallic boards for the top, bottom and sides, in combination with metal slide corners adapted to lock thelongitudinal edges of the boards, said corners each comprising a metal strip having complemental return bends to interlock when the boards are slid longitudinally with relation to each other, the strips on the side boards being adapted to and assembly any new or additional dimensions 5. In an air duct according to claim 1, the combination of a top board resting on the upper edge of the side board and a projection from the lower'face of the top board adjacent the inner face of the side board adapted to prevent collapse of the corner. i

6. In an air duct according to claim 1, the provision of screws fastening the metal strip to the top board which project downwardly beyond the top board inline with the side board to prevent collapse of the corner, substantially as described.

7. In an air duct according to claim 1, the combination of a back-up strip on the inner side of the upper edge of the side board, adapted to underlie and support the top board, and screws projecting downwardly through the top board in juxtaposition with the edge of the said back-up strip to prevent relative movement of the side and top boards.

8. An air duct for heating, ventilating or air conditioning systems, comprising non-metallic boards for the top, bottom and sides, in combination with metal strips projecting outwardly and mounted on edges of said boards and also forming joints between the boards transverse of receive the edge of the top board between their return bends and the edge of the side board, the transverse joints between the boards being offset in the sides of the duct with relation tothe'top and, a on nation with metal slide corners, adapted to lock the longitudinal edges of the boards, said corners each comprising complemental metal strips having return bends adapted to interlock when the length of the duct, said joints being offset as between the sides and the top and bottom, the

metal strips being formed so asto permit assembly of the boards by sliding eachboard and the strips mounted on it longitudinally past the joints of the adjacent faces of the duct.

9. A fitting for an air duct for heating, ven

facing toward the leg fastened to the board, but

not reaching it, substantially for the purposes described.

10. A fitting for an air duct for heating, ventilating or air-conditioning systems, in which the top, bottom and sides of the duct are made of non-metallic boards, comprising a strip adapted to be fastened to one side of an edge of one of the boards, a metal strip adapted to be attached to the other side of the edge, both said strips beingbent parallel to said edge substantially in the plane of said edge and projecting beyond one and the same face of the board, said two projecting portions being spot-welded together, and a projection on one of said strips beyond said firstmentioned projecting portions extending parallel to the face of the board and adapted to be bent into parallel relation with said two projecting portions and toward said board, as and for the purposes described.

V 11. A fitting for an air duct for heating, ventilating or air-conditioning systems, in which the top, bottom and sides of the duct are made of non-metallic boards, comprising a doubled metal the boards are slid longitudinally with relation to each other, the strips on the'side boards being adapted to receive the edge of the top board between one of their return bends and the other return bend and the edge or the side board, and a back-up strip on the inner side of the upper edge of the side board adapted to underlie and support the top board.

strip with its main portion lying substantially in the plane of anedge of one of the boards and projecting to one side of said edge, one leg of said fitting being adapted to lie against one face of the board and the other leg being adapted to lie against the other face of the board, as and I for the purposes described.

FRANK J. TOWNSEND. 

